A new NIH-funded study has identified a major change in the immune environment of the hippocampus, the part of the brain involved in learning and memory, according to ScienceDaily. Researchers say the shift appears to begin in midlife and may help explain how aging contributes to the long-lasting brain inflammation seen in some neurodegenerative diseases.
The team, led by scientists from the University of California, San Diego, the New York Genome Center and the University of California, Irvine, studied postmortem hippocampal tissue from 40 neurologically healthy adults ages 20 to 95. Using advanced single-cell techniques, they examined both gene activity and the genome’s 3D structure and chemical modifications.
The analysis found that microglia, the brain’s main immune cells, gradually decline from about age 50 to 75. At the same time, they appear to be replaced by cells with stronger inflammatory signals and traits similar to immune cells that come from peripheral blood, challenging the long-held view that microglia simply remain in the brain and renew themselves throughout life.
Researchers also found signs of age-related decline in cells that help maintain the blood-brain barrier, along with widespread changes in genome organization across many brain cell types. The study’s authors say future research will look at why resident microglia are lost with age and whether the newly identified immune transition contributes to Alzheimer’s disease and other age-related neurological conditions.
